HDD, Duckbill Valve and Air Valve

[sunami]

I have 3 questions and wonder if someone here can help:

1. I need to lay a sewage rising main in a winding footpath. Can HDD adopt a meandering alignment from one single drill pit?
2. What is typically the head loss coefficient of a Rubber Flex Slip-In In-Line Duckbill Check Valve and a Low Head Loss In-Line Duckbill Check Valve?
3. When pumping past an air valve, is it required to ensure there is at least a 1m head above the air valve, rather than measuring from the invert level of the pipe? I'm particularly curious about how this applies when dealing with larger pipes, such as those with a diameter of 1m or more. What’s the best practice for ensuring proper operation in these cases?

Thanks.

 

[coloeng]

Answer to Question 1: Yes, HDD can do a meandering path from one drill pit. A caveat is that the degree of meander is controlled by the diameter of the drill rod. Additionally, the more meanders the higher resistance to pull-back on the pipe and the larger machine that is required, which in turn can increase the diameter of the drill pipe. You should contact an HDD contractor that specializes in this type of construction.

 

[sunami]

Answer to Question 1: Yes, HDD can do a meandering path from one drill pit. A caveat is that the degree of meander is controlled by the diameter of the drill rod. Additionally, the more meanders the higher resistance to pull-back on the pipe and the larger machine that is required, which in turn can increase the diameter of the drill pipe. You should contact an HDD contractor that specializes in this type of construction.

Thanks.

 

[bimr]

2. Contact the manufacturer. https://www.cla-val.com/waterworks/rubber-flex-duckbill-check-valves

3. For an air release valve, depending on the specific design, the minimum sealing pressure can be as low as around 0.2 bar, allowing it to seal effectively even in low-pressure situations within a piping system; however, the exact minimum pressure will vary depending on the valve manufacturer and application.

 

[sunami]

2. Contact the manufacturer. https://www.cla-val.com/waterworks/rubber-flex-duckbill-check-valves

3. For an air release valve, depending on the specific design, the minimum sealing pressure can be as low as around 0.2 bar, allowing it to seal effectively even in low-pressure situations within a piping system; however, the exact minimum pressure will vary depending on the valve manufacturer and application.

Thanks.

 

[sunami]

Thanks.

I received a response from Cla-Val with the data sheet for the duckbill check valves, showing some charts on head loss versus flow rate. After conducting my analysis, I calculated a head loss coefficient (K value) of 7.0 for the slip-in type and 8.7 for the low head loss type. The results seem off to me. I wonder if anyone here could help spot any errors in my calculations. Alternatively (let me ask again), does anyone here know what the K value should be for a slip-in duckbill valve and a low head loss duckbill valve? Thanks.

 

[bimr]

Your calculated result of the k value is in the range of what one would expect.

Don't know why you are putting such a thorough review for a check valve headloss as the headloss through a check valve is a minor headloss and can be ignored for the most part.

I also don't understand why you are even using the duckbill as it seems to be misapplied here. Duckbill check valves are typically used in low head applications like tidal gates. Duckbill check valves may not have the same reliability as a swing check valve in higher pressure applications and may not close as quickly either.

 

[sunami]

This project of mine involves augmenting the existing sewage pump station (SPS) with a second sewage rising main. Namely, the SPS already has a rising main and my client wants to add a second one as standby. As the standby rising main could sit idle for a long time (say years), septicity is an issue if sewage backflows into it. I therefore want to place a Slip-In In-Line Duckbill Check Valve at the discharge end to prevent backflow, but I can't find the head loss coefficient (K value) anywhere.

 

[pointsman]

This cut sheet contains charts showing headlosses for valves of this type.

https://www.redvalve.com/uploads/02_09_21_Revised_Brochures/The_Tideflex_Duckbill_Check_Valve_Advantage_Brochure_RV09.00-1_040424.pdf